4. Aquatic habitats in Amazonia

4. Aquatic Habitats in Amazonia WOLFGANG J. JUNK

ConvOnio Max-Planck-Institu t fiir Limnologie, Abt. TropenOkologie, Pldn, Germany and Instituto Nacional de Pesquisas da AmazOnia (INPA), Manaus, Brazil

Introduction

Existing Attempts of Classification

The Amazon river and its tributaries are the greatest river system on earth. High yearly precipitation rates, between 2000 mm and 3000 mm in most parts of the catchment area, result in a mean discharge o f the Amazon of 175 000 m 3 per s (without Rio Tocantins). This discharge is more or less one sixth of the total discharge of all rivers on earth to the oceans (Oltman et al., 1964; Sternberg and Parde, 1965; Oltman, 1967). Considering a catchment area o f about 7 0 0 0 0 0 0 km 2, the number and variety of waterbodies is very large. It is of interest to group these into a small number of categories, based on important characteristics, to facilitate the work of ecologists. Tentative classifications have already been made, using various criteria such as hydrochemical, production-biological and biological parameters. However, most refer to some specific waterbodies only, or are based on criteria which do not show the great variety of aquatic habitats found in Amazonia. These attempts will be discussed later and an additional approach will be proposed based principally on hydrological and morphological criteria, having a decisive influence on the limnology and using easily identifiable units. These units are not necessarily in the same ecological order of precedence; some are easily defined as habitats whereas others have to be considered as a complex of habitats or even as ecosystems. Based on this classification, our state of knowledge about frequency, distribution and ecology of the different units established will be discussed and reference made to some of the extensive literature. Furthermore, human impact and their vulnerability to it will be evaluated. This tentative classification does not claim to be complete or even generally accepted but because of the limited state of knowledge about aquatic habitats in Amazonia, it should serve as a basis for discussion.

Physico-chemical Classification

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The first attempt to classify Amazonian waterbodies was based on differences in water colo.ur. Names like Rio Preto, Rio Branco, Rio Verde indicate that this type of differentiation has been used by the people for centuries. Sioli (1950, 1965) established three different 'water types', based on water colour and physico-chemical parameters: 'White water' is rich in inorganic suspensoids, is turbid and has a pH value of about 7. The concentration of dissolved minerals is relatively high. 'Black water' is rich in dissolved humic substances, has a dark brownish colour and is transparent. The pH value is extremely low, about 4. The concentration of dissolved minerals is very low. 'Clear water' is greenish and transparent, the pH value ranging between very acid and neutral. Concentration of dissolved minerals may range from very low to relatively high. The transition between these water types is fluent. Recent studies (Furch, 1976; Furch and Klinge, 1978; Junk and Furch, 1980; Furch et al., 1982) show that white water is a carbonate water with a high percentage of alkali-earth metals, whereas black water is a non-carbonate water with high percentage of alkali metals. Clear water generally is non-carbonate water, but may be carbonate water, as well, for example in carboniferous areas. The classification of Amazonian waters by hydrochemical parameters is not yet satisfactory. Detailed studies, already underway, will increase our knowledge considerably in the next years, and will possibly allow more detailed correlation between the geology of the catchment area and the hydrochemical conditions in the water. Such a classification has to be considered as a very important contribution to the definition of aquatic habitats and ecological niches in Amazonia.

Biological Classification Attempts at biological classification are only beginning and are partly based on physico-

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chemical classifications. From the point of view of production biology, Amazonian waters can be classified as highly productive, medium productive and low productive; since they are autochthonous primary production is the basis for this division. It corresponds to the hydrochemical classification of Sioli (1950). White water is of high productivity, clear water of medium to low productivity and black water of low productivity (Sioli, 1968; Schmidt, 1973b, 1976, 1982). Fittkau's ecological division of the Amazon basin (1974) is based on this classification. However, there exist great differences in primary productivity, even under hydrochemically equal conditions, because other factors influence production rates. Light, for example, may be the limiting factor in strongly shadowed forest creeks, whereas it is not in savannah creeks. Heavy turbidity and water colour have a strong influence on phytoplankton production. How far primary production rates correspond to secondary production is not yet sufficiently known. Food webs may be based on allochthonous material. This has been shown for the fauna of extremely nutrient-poor forest creeks of Central Amazonia. The fish fauna is astonishingly well represented, terrestrial insects and plant material forming much of its diet (KnSppel, 1970; Soares, 1979). For the big rivers this classification in very general terms works. Additional investigations are necessary and complete fisheries statistics of the principal parts of the Amazon will improve our knowledge. Characterisation of waterbodies by key organisms is not yet possible. However, Sioli (1953) indicates that hydrochemical parameters like low pH values and/or low concentrations of dissolved minerals, principally lack of alkali-earth metals in black water and in some clear waters, have impacts on the distribution of molluscs. Geisler et al. (1971 ) and Roberts (1972) in dicate possible eco-physiological impacts of the hydrochemical conditions on the fish fauna, and Junk (1970) does this for some aquatic macrophytic communities. Reiss (1976b, 1977) discusses a characterization of central Amazonian lakes in respect to the macrobenthos fauna, whereas Rai and Hill (1980) use microbiological and physio-chemical characteristics. Actual studies in the floodplains indicate that a classification of habitats may be possible based on the fish fauna. Species composition is strongly influenced by several factors, for instance food availibility, shelter and current. A very important factor seems to be oxygen concentration which depends on lake morphology and Vol. 3 (1983) Supplement No. 5

production-biological conditions (Junk et al., 1983). However, the problems are very complex and not yet fully understood.

Characterization of Amazonian Waterbodies by Morphological and Hydrobiological Characteristics Rivers Rivers are one of the most impressive manifestations of aquatic ecosystems in Amazonia (Fig. 4.1). All rivers are influenced by strong waterlevel fluctuations. Maximum flooding is reached in the southern affluents earlier than in the northern ones, the period with highest waterlevel in the south being February to April, and in the north June to August. In the Amazon, flooding reaches its maximum normally at the end of June. Waterlevel fluctuations decrease in the Amazon from the Andes to the mouth, being between 16-20 m at Iquitos, 8 - 1 5 m at Manaus, and on the lower courses about 4 - 6 m. Regular measurements of waterlevel exist only for the Amazon itself and its most important affluents (Salati, 1975). Studies of the river morphology have been carried out by Sternberg (1960), Sioli (1967) and Irion (1976). They show that the river valleys were strongly influenced by the fluctuations of the sealevel during the ice-ages. Data about hydrochemistry exist principally about the Amazon and the Rio Negro (Gibbs, 1967; Anon., 1972; Schmidt, 1972a; Leenheer and Santos, 1980; Stallard, 1980). For most of the large affluents, little information is available (Gibbs, 1967, 1972; Stallard, 1980). Rivers are open ecosystems with a discharging character. Huge amounts of material are transported by them to the sea; the quantity of carbon transported by the Amazon is calculated as 100 million tons per year (Richey e t al., 1980; Richey, 1982). These quantities have to be considered as they are important for the balance of elements of the whole planet (Schlesinger and Melack,1981 ). Biological and ecological information exists about some of the rivers, principally about fish fauna, because of the great importance of inland fisheries (Junk and Honda, 1976; Petrere, Jr., 1978a, b; Goulding, 1979; Bayley, 1981 ; Worthmann, 1982). However, additional studies are very important because of the increasing fishing effort resulting from rapidly growing population. Over the next years, some of the big affluents of the Amazon will suffer from strong human impact. Modifications in the catchment areas may

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Fig. 4.1. Manu River inside National Park, Peru 1974, as seen from plane (Photo credit: Dr H. Jungius).

change the amount of discharge, sediments, suspensoids and dissolved substances. Lack o f baseline data will make it very difficult to detect such modifications. For example, Nordin and Meade (1981) criticize data on a change in the discharge of the Amazon by Gentry and Lopez Parodi (1980) because of the inadequacy of the data. The construction of huge hydroelectric p o w e r plants will have a direct impact on several o f the big affluents of the Amazon. Tucurui, a manmade lake on the Rio Tocantins, will cover an area of 2300 km 2. Many other reservoirs are in construction or are being planned. Additional impacts may result from industrial pollution, for example by great amounts o f red mud or other industrial wastes put into the rivers, and by pesticides from agriculture. These impacts will not only affect the respective affluents but connected habitats as well, such as the floodplains, the main river and even coastal areas, as will be shown later. Several projects about sediment load and transport of dissolved substances of the Amazon and its main tributaries are underway and will help to increase our knowledge. Creeks

The Amazon Basin has the greatest density of creeks on earth (Fig. 4.2). The total area occupied by the creeks may be much bigger than the area 26

occupied by the big rivers themselves. Unfortunately, there is a tendency to consider all the creeks as a whole. It is a very big simplification to consider all creeks as one ecologically uniform habitat. Differences in hydrochemistry have already been indicated. Other differences can be shown in respect to solar irradiation. Creeks in the Campo Cerrado are little shadowed by a gallery forest and are strongly colonised by aquatic macrophytes, whereas forest creeks in Central Amazonia are lacking most of these species, probably because of lack of light. Ecological differences are supposed to exist between perennial and temporary creeks. The fish fauna of creeks with rapids is quite different from the fauna of slowly running creeks in the lowlands. Other differences are to be expected in respect to the creeks in the Andes which also belong to the Amazon Basin. Studies of rivers and creeks in temperate regions have shown a zonation which allows a division into areas of springs, upper, medium and lower course (Illies, 1961 ; Illies and Botosaneanu, 1963). These areas can be characterized limnologically as well as by the ichthyofauna. This may be different in Amazonian lowland creeks, because temperature does not change as it does in temperate regions. But there may exist other important ecological factors, for example oxygen content, if we differentiate between bank areas, The Environmentalist

Fig. 4.2. Example of a creek (Photo credit: Dr E. J. Fittkau).

ground water inputs, accumulation of leaves or mud, etc. Considering these aspects, creeks are very complex systems of different habitats (Fittkau, 1973, 1976; Soares, 1979). This is indicated by a huge species diversity. Knoppel (1970) determined in a reach o f 300 m o f a little forest creek of 1 - 2 m width about 40 different fish species. Compared with this, an inventory of the fish fauna in a reach o f 100 km o f Rio Tocantins, a very big affluent of the Amazon, has shown until now little more than 150 species (M. G. M. Soares, pers. comm.). Even supposing that this number will increase up to 200 species, the species diversity in the small creeks is astonishing. The fish fauna of creeks is relatively welldocumented. However, considering the fact that until n o w 1500 freshwater fish species are known to science, and about 2000 species are supposed to exist in Amazonia, our knowledge is limited. Other animal groups, like aquatic insects, are very little known. An increasing amount of information exists about hydrochemistry (Schmidt, 1972b; Furch, 1976; Junk and Furch, 1980). Recent studies Vol. 3 (1983) Supplement No. 5

may lead to a hydrochemical classification o f creeks in relation to the geology of the respective catchment areas. The importance of such a classification has already been stressed. Considering their small size, creeks have to be considered as very vulnerable to human impact. Deforestation and pollution will change the hydrology (Salati, 1978) and hydrochemistry, and consequently the plant and animal communities to a much greater extent than, for example, the actual collection of ornamental fish. Therefore, intensive studies on specific creek systems are very important. Such studies started some years ago. Furthermore, comparative studies are necessary to determine h o w far creeks are ecologically uniform, and if they have individual aspects. Without this information n o b o d y knows which creeks to protect, where to protect and how to protect them.

Waterfalls Waterfalls are very special habitats. The colonizing fauna and flora have to be adapted to high current speed, rocky substrate, living in part in an 27

air-water interspace. Waterfalls are known as typical localities for Podostemonaceae, a highly specialised family of aquatic macrophytes. Beside this, waterfalls may be a barrier for the fauna, inhibiting upstream migrations and gene-flow. In Amazonia, waterfalls exist mostly in the area of the archaic shields of the Guianas and Central Brazil and the Andes. Little is known about their importance as a fauna barrier. Because of their beauty, they should be protected as national monuments.

Deep Closed Lakes Deep closed lakes are accumulating systems. They show special limnological conditions like physical, chemical and biological stratifications. Because o f their age and lack of communication with other aquatic systems, they favour the development of endemic organisms. Deep lakes with more or less closed lake basins are rarely found in Amazonia. This is probably due to the geology of the region. The Amazon Basin is the greatest tertiary sedimentation area on earth. Depressions, which could have led to the building of lake basins, were filled up with sediments during the tertiary. Later on tectonic movements did not affect the basin, except in the Andean region. During the ice-ages, the decrease of the sealevel by about I00 m resulted in deep fiver valleys. With a rising sealevel, the valleys in Central Amazonia were flooded and actually represent lakes in the non-floodable 'terra firma' area. They are called 'lagos de terra firme' or 'ria lakes'. These lakes are black and clear water lakes. White water rivers have already filled up their valley with sediments. However, ria lakes have only in part the character of real lakes, and have to be considered as a part of a river with the more or less well developed characteristics of a lake. Probably the only real deep closed lake basins in the Brasilian part of Amazonia occur in the mountains of the upper Rio Negro, called 'Morro de 6 lagos'. Air photographs show six little closed lake basins. The geology of this area differs considerably from the general pattern. There is no information about the lakes, because access is very difficult. In the Andes, some deep closed lakes may also occur. Shallow Lakes In the literature the term 'shallow lakes' includes all shallow waterbodies as well as manmade lakes. I prefer to differentiate between closed and open shallow lakes, because they show clear ecological differences, which will be discussed in the respective chapters.

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Closed shallow lakes Closed shallow lakes are very common in the savannah area of Roraima. They are in part perennial, in part temporary and attract attention by their regularly round shape. Reiss (1973) explains their origin and shape by wind erosion. Most of these lakes are supplied by rainwater and consequently the water is very poor in dissolved minerals and very transparent. The fish fauna is very poor in species because of the severe droughts, which affect the area from time to time. Generally, the lakes have to be considered as oligotrophic. However, they may become eutrophic, showing a beautiful number and variety of water birds. Swampy areas, colonized by Cyperaceae may occur. Our knowledge about these habitats is completely insufficient. Human impact seems to be limited to eutrophication effects by cattle raising. Open shallow lakes (floodplain lakes) Floodplain lakes are shallow lakes which are connected with the rivers at least during some period of the year. They receive a part of their water from the river, when the flood comes, and devolve it when the water goes down. Combined with the water exchange is the exchange of nutrients, energy and biological material. This has a very strong impact on the lakes, on the river and on the whole floodplain. According to Hutchinson (1957) floodplain lakes include oxbow lakes, lateral levee lakes, lakes in abandoned channels, lakes in depressions formed by uneven aggregation of sediments during flood, and others. These lakes can be considered as intermediate between closed lakes as accumulating systems and rivers as discharging systems. Most of these lakes are subjected to high waterlevel fluctuations and great periodic modifications in area. The limnology of floodplain lakes and their colonising organisms around Manaus is relatively well-known (Marlier, 1965, 1967, 1968; F6rster, 1969, 1974; Junke, 1970, 1973; Koste, 1972; Schmidt, 1973a, b; Reiss, 1976a; Uherkovich, 1976; Uherkovich and Schmidt, 1974; Brandorff, 1977; Fisher, 1978; Ribeiro, 1978; Rai, 1979; Rai and Hill, 1980; Santos, 1980; Martins, 1980; Hardy, 1980; Carvalho, 1981; and many others). Additional information will be elaborated by several existing projects about limnology, ichthyology and fisheries. A detailed study about the limnology of some floodplain lakes on the lower Rio Tapajos was made by Braun (1952). The importance of floodplain lakes and the impact of human activities will be discussed in the following chapter. The Environmentalist

Floodplains The differentiation between floodplain lakes and floodplain may be surprising since during high water the whole area is inundated. However, on the organisation level of habitats, such a differentiation seems justified. Whereas floodplain lakes are habitats of an aquatic character, the floodplain has during certain periods aspects of a terrestrial habitat. Doubtlessly, there is no sharp definition for both, because of the waterlevel fluctuations. However, the biological consequences are evident. The typical floodplain forest of the middle Amazon occurs, for instance, mostly in the higher parts of the floodplain, because it needs a certain period of drought. Many species cannot grow in areas which are permanently flooded. However, there is a special type of forest which obviously tolerates permanent flooding (Prance, 1980). In how far the differentiation between floodplain lakes and connected rivers can be made, will depend on definitions and the viewpoint of the scientist. Welcomme (1979) considers, in respect to fisheries, rivers, lakes and connected floodplains as one unit. This may be true for many fish species which migrate between river and floodplain. However, considering terrestrial game animals, we may consider the floodplain as in part pertaining to the nonfloodable terrestrial system. Junk (1980) describes floodplains as transitional systems between aquatic and terrestrial ones. The great number of morphological, physiological and/or ethological adaptations of floodplain organisms on the change between both phases as well as the complex nutrient cycles in the floodplains seem to justify it. In spite of their enormous area, covering in the Amazon Basin alone more than 100 000 km 2, floodplains are very little studied. Obviously, the change between terrestrial and aquatic phase creates a problem for scientists (Bayley, 1980; Junk, 1980). It signifies a change between limnology and terrestrial ecology, including a fundamental change in methodology. Relatively good knowledge exists about hydrophytes (Junk, 1970; Howard-Williams and Junk, 1976, 1977; Junk, 1982a) and fishes (LoweMcConnell, 1975; Smith, 1979; Goulding, 1980). Several ecological studies exist about the invertebrates living during the terrestrial and aquatic phases (Beck, 1969; Irmler, 1975, 1976, 1981; Adis, 1979; Irmler and Furch, 1980; Irmler and Junk, 1982). However, there are great taxonomic problems, 80% of new species in one family are frequent. Investigations on the ecology of floodplains started some years ago and will increase our knowledge. There is an urgent need for further Vol. 3 (1983) Supplement No. 5

information, because floodplains have been declared in the whole of Brazil as areas of intensive colonization efforts for utilization by agriculture and husbandry. These projects are financed by the 'provfirzea' programme of the government. In the Amazon Basin utilization of the floodplains of white water rivers (vfirzeas) can be justified because they belong to the best soils in the whole area (Camargo, 1958; Sternberg, 1960; Sioli, 1969; Petrick, 1978; Junk, 1979, 1982b). Floodplains of black water rivers have very little potential for agriculture and husbandry. Their utilization would create great damage to the ecosystem without long-term economical benefits. Floodplains of clear water rivers may have intermediate status. An overlap of interests may occur with fisheries, which is practised in the same area. A more detailed analysis of this very complex situation is given by Welcomme (1979) and Junk (1982b). Ecologists have a real chance to influence the development planning in the vgrzea, when they are able to propose economically feasible alternatives. This is due to the fact that the population density in the floodplains is still very low and there exists very little infrastructure. Once big projects are started, including for example the construction of big and expensive flood control measures, a modification of the development scene is nearly impossible. Other impacts floodplains may suffer derive from the connected rivers. A hydroelectric power plant, for instance, will affect the waterlevel fluctuations and sediment load of the water and change the ecological conditions in the connected floodplains, as has been shown on the River Nile after construction of the Aswan Reservoir. River pollution will also affect the floodplains and may have long-term effects on fauna and flora. Residues of papermills, for instance, containing mercury, will be deposited in the floodplains during high water and may contaminate the terrestrial fauna and flora, as well as the aquatic ones, for many years.

Swamps Swamps are areas where the groundwater table reaches the surface most of the year, or where the soil is little flooded. Such areas occur in Central Amazonia mostly along the creeks and small rivers. They are built by the precipitation which comes down from the slopes of the valleys. The waterlevel of the creeks and small rivers is. strongly influenced by local rainfall, which may create short-term floods of the adjacent swamp areas. The local name of such areas is 'buritisal', 29

according to a characteristic palm growing there, the buriti (Mauritia flexuosa). In Central Amazonia much more than 1 0 0 0 0 0 km 2 are covered by such areas. Very little is known about their ecology. Hydrological data are being collected.

Permanent Periodic Waterbodies The high amount of precipitation results in a great number of permanent and periodic small waterbodies, like pools, phytotelmes, etc. Although small and of little attraction for scientists, their importance as aquatic habitats should not be underestimated. They are colonised by many insects with short life cycles and are used by frogs for spawning and living. The fact that some of the insects transmit diseases like malaria, or are troublesome like mosquitoes, underlines the need of studies from a practical point of view. Whilst little is known about them, experimental studies are actually in progress.

Sub terranean Waters Subterranean waters are represented in Amazonia only by groundwater and interstitial water. Subterranean creeks or lakes do not exist because of the geology of the area. Information about subterranean waters in Amazonia is very limited. However, studies on the age, movements, position, etc., of groundwater are very important, because large scale deforestation has a strong influence on the groundwater table and may indirectly affect the whole system. Considering the fact that modifications may show up only after a period of time, and natural fluctuations may occur because of the seasonality of precipitation, base line data are of great interest.

Brackish Coastal Waters Brackish coastal waters occur in large areas in the m o u t h areas o f the Amazon River. Unfortunately, information about these habitats is insufficient to permit a detailed consideration here. However, from other brackish water regions in the world, the biological and ecological importance of such habitats and their relationship with inland waters as well as with the sea are well documented. Detailed studies in Amazonia are very important, because the great human impact on its big affluents may in the next decades change the hydrological and hydrochemical regime of the Amazon itself to a degree that it influences the coastal waters. Therefore, there is an urgent need for base line data. 30

Artificial Waterbodies It may seem strange to include artificial waterbodies in a discussion about aquatic habitats of Amazonia. However, in future such artificial habitats will occur in increasing numbers all over the basin. An understanding of the modification of artificial waterbodies will help us to understand the natural ones if we use artificial waterbodies as large scale experiments. Some ecologists believe that such investigations will be misused for political and economic purposes. In my opinion, we should not lose the possibility to get a maximum of information, because only with sufficient knowledge can alternatives be considered and negative side effects minimised.

Man-made Lakes In the next decades, several big hydroelectric power plants will be built in Amazonia, like for instance, Tucurui on the Rio Tocantins (2300 km2), Balbina on the Rio Uatum~ (2100 km2), Samuel on the Rio Jamari (645 km2), Porteiras on the Rio Trombetas (1400 kin2), Babaquara and Carar~o on the Rio Xingu (6100 km z and 1200 km 2, respectively), and so on. There is no d o u b t that those gigantic constructions in combination with connected industrial projects will affect not only the rivers directly involved, b u t also the ecology of great neighbouring areas. A discussion about the necessity and the benefits of these projects is not possible, because it would include economic, political and other aspects. In respect to the impact o f these big man-made lakes on the rivers, it is likely to be detectable not only in the area directly affected, but as well in the areas upstream and downstream. Dams will be constructed on several very large affluents of the Amazon and the impacts on the discharge and sediment load of the main river and even on the coastal areas cannot be excluded. However, about the dimensions of such impacts nothing can be said specifically. Today, only two small manmade lakes exist in Amazonia: Pared~o, north o f Belem, and Curu~-Una, south of Santarem. They cover about 100 km 2 and produce 40 mW each. A b o u t Pared~o there is no information available, whereas Curufi-Una has been studied for 4 years (Junk et al., 1981 ; Darwich, 1982; Junk, 1982c). These studies show that several negative side effects can be expected, which have been observed in other tropical man-made lakes in Africa and Asia. These effects include, for instance, changes in the fish fauna, mass development o f aquatic macrophytes and deterioration of water quality, principally high oxygen deficit. For two years, about 20 manatees (Triehechus inunguis) The Environmentalist

have been introduced into the lake as a tentative biological control of the macrophytes. Even supposing there is only some effect on the macrophyte vegetation, this change probably offers a new habitat for a species in danger of extinction. Unfortunately, studies in Curufi-Una have only been started after the construction of the dam. Therefore, a direct comparison with the former conditions is not possible. This problem has been avoided in Tucurui where intensive studies began before damming up the river. These studies are concerned both with the aquatic habitats as well as the terrestrial ones. Fish Ponds At present, fish ponds exist in Amazonia only in a very limited number, because fish culture is not yet economically feasible due to the lack of know-how. This situation will change in the next decade (Saint-Paul and Werder, 1977; Junk, 1979; Saint-Paul, 1982; Werder and Annibal, in press). Fisheries can no longer offer enough fish at low prices to a rapidly growing population. Therefore, fish culture will be of increasing importance for protein production. Besides affecting lakes, swamps and creeks by the construction of the ponds, fish culture may create two big problems for the native fauna: (1) The distribution of fish and fry may distribute diseases and parasites, and (2) The introduction of exotic species may affect the native fauna, when such species escape and become adapted to the new habitats. Over many years, tilapias have been grown in Amazonia and have escaped into natural waters. Obviously, they did not become adapted to the new habitats. However, this problem has to be observed carefully. The best means of avoiding the introduction of exotic species for fish culture is in my opinion, the development of sufficient knowledge about the culture of high price native species. More studies of this are needed. Rice Fields The cultivation of rice in Amazonian wetlands is still in the beginning. The largest plantations were started some years ago in the Jari project. However, information about the ecological consequences of large scale rice plantations is not available. Studies in South East Asia have shown that rise plantations represent very complex habitats (Heckman, 1979). They may have negative side effects because of the need to apply pesticides and the propagation of water-borne diseases, like schistosomiasis. On the other hand, combined rice and fish cultivation is one of the most lucrative agricultural activities in South-East Asian wetlands. In the state of Amazonia, experiVol. 3 (1983) Supplement No. 5

merits with rice cultivation in the vfirzea have been started recently. Comparative ecological studies should accompany them to get the necessary information. Pools and Wastewater Human activities create small waterbodies everywhere. In Amazonia, they can be observed in great numbers, for example along the roadsides of the big highways like the Transamaz6nica and the South-North connection. They indicate the places where material was collected for road construction and which later on were filled with rainwater or groundwater. Around villages highly polluted pools and even wastewater pools occur. These are very important artificial habitats which serve for the distribution of plants and animals, including parasites and diseases. During the rainy season, the ditches along the highway between Porto Velho and Manaus, for instance, facilitate the distribution of aquatic organisms for many kilometers without interruption. The control of malaria and mosquitoes will depend in part on our knowledge about the ecology of such habitats, but detailed information is lacking.

Protection of Aquatic Habitats It seems generally accepted that the protection of the terrestrial environment automatically includes an adequate protection of aquatic habitats. In fact this is not the case. The discussion about the creation of National Parks or other types of protected areas in Amazonia is based principally on the theory of refugia. In accordance with actual knowledge, areas which are considered as refugia of several groups of species are of high priority of protection (Wetterberg et al., 1976; Wetterberg and Pfidua, 1978; Wetterberg etal., 1981). However, it has to be stressed that the theory of refugia is based only on the distribution pattern of some terrestrial plants and animals. There are no studies about their applicability to aquatic organisms and systems. Very probably the big river systems of Amazonia have been affected only to a limited degree by climatic changes which are supposed to be the reason for the formation of refugia. Even supposing a change in total discharge and the pattern of waterlevel fluctuations, the existence of the river systems as such was not affected. Therefore, climatic changes may have had relatively little influence on the aquatic fauna and flora. There are several problems in protecting river systems or parts of them. River banks and floodplains are relatively 31

densely c o l o n i z e d a n d utilized b y agriculture, h u s b a n d r y and t i m b e r e x t r a c t i o n . T h e rivers t h e m s e l v e s are used b y n a v i g a t i o n , fisheries and, in f u t u r e , in s o m e cases b y h y d r o e l e c t r i c p o w e r plants. T h e r e f o r e , t h e y have to b e c o n s i d e r e d as areas o f m u l t i p l e interests, w h i c h overlap with c o n s e r v a t i o n interests. H u m a n i m p a c t s o n the river, such as p o l l u t i o n or changes in discharge and s e d i m e n t load o u t s i d e the p r o t e c t e d areas, m a y a f f e c t d i s t a n t p r o t e c t e d areas. F u r t h e r m o r e , rivers and creeks h a v e to b e considered as ' o p e n s y s t e m s ' w h i c h t r a n s p o r t organisms b y drift or allow active m i g r a t i o n s o v e r long distances. M a n y c o m m e r c i a l l y e x p l o i t e d fish species have large feeding and s p a w n i n g migrations, which are n o t y e t fully u n d e r s t o o d . S e m a p r o c h i l o d u s spp. and B r y c o n spp. for instance, m i g r a t e f r o m the p r o t e c t e d areas o f Analvilhanas, an archipelago in the l o w e r Rio Negro, to the A m a z o n f o r spawning. Soon a f t e r leaving the p r o t e c t e d area, t h e y are caught in great quantities. N o b o d y k n o w s y e t if the s p e c i m e n s which m i g r a t e b a c k t o the Anavilhanas b e l o n g to the same s t o c k or are c o m i n g at least in p a r t f r o m o t h e r a f f l u e n t s o f the A m a z o n . Since such m i g r a t i o n s m a y e x c e e d h u n d r e d s o f kilom e t e r s , t h e r e are n o N a t i o n a l Parks big e n o u g h to p r o t e c t t o t a l l y these m e m b e r s o f the fish fauna. T h e r e f o r e an a t t e m p t should be m a d e to p r o t e c t w e l l - d e t e r m i n e d aquatic h a b i t a t s , including watersheds, in d i f f e r e n t sections o f the big rivers, f o r i n s t a n c e in specific lake s y s t e m s in the f l o o d p l a i n s or islands in the river channel. These m e a s u r e m e n t s w o u l d p r o t e c t the characteristic l a n d s c a p e , the flora and the m o r e s t a t i o n a r y species o f animals, whilst migrating species w o u l d have at least t e m p o r a r y p r o t e c t i o n . Several relatively small areas m a y be m o r e effective t h a n a single very big one. A specific legislation m a y regulate fisheries. A d d i t i o n a l l y , highly v u l n e r a b l e aquatic species, f o r e x a m p l e the m a n a t e e ( T r i c h e c h u s inunguis), the big turtle (Podocnernis expansa), the giant o t t e r (Pteronura brasiliensis) m u s t be p r o t e c t e d b y special laws ( J u n k , 1975; A y r e s and Best, 1979). O t h e r a q u a t i c h a b i t a t s are easier to p r o t e c t , b e c a u s e t h e y are o f smaller size. In p a r t t h e y are already i n c l u d e d in the existing N a t i o n a l Parks and o t h e r p r o t e c t e d areas. H o w e v e r , a d d i t i o n a l studies o f the aquatic f a u n a a n d flora are n e e d e d and will in f u t u r e indicate f u r t h e r specific waterb o d i e s f o r p r o t e c t i o n . In this r e s p e c t it has to be stressed, t h a t an a d e q u a t e p r o t e c t i o n o f a q u a t i c h a b i t a t s m u s t include the p r o t e c t i o n o f the respective watersheds, to g u a r a n t e e the m a i n t e n a n c e o f its specific c h a r a c t e r . 32

Summary D i f f e r e n t existing c o n c e p t s for the classification o f A m a z o n i a n w a t e r b o d i e s are discussed. An a d d i t i o n a l a p p r o a c h is suggested to c h a r a c t e r i z e a q u a t i c h a b i t a t s , b a s e d o n h y d r o l o g i c a l and m o r p h o l o g i c a l p a r a m e t e r s . T h e state o f k n o w l e d g e a b o u t the f r e q u e n c y , d i s t r i b u t i o n and e c o l o g y o f a q u a t i c h a b i t a t s is discussed. H u m a n i m p a c t s on a q u a t i c h a b i t a t s in A m a z o n i a and their vulnerability to t h e m are evaluated.

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XVIII Congries Internaeional de Geographie, Tome Second, Rio de Janeiro, pp. 3 9 9 - 4 2 4 .

The Environmentalist